Pressure ring assembly

Abstract

A pressure ring assembly is disclosed, comprising a pressure ring segment and a contact shoe that is displaceably connected to the pressure ring segment. A cavity is formed between the pressure ring segment and the contact shoe. The pressure ring assembly is configured without a contact pad between the pressure ring segment and the contact shoe, thereby simplifying the structure and potentially enhancing performance.

Description

[0001] PRESSURE RING ASSEMBLY

[0002] BACKGROUND TO THE INVENTION

[0003] The invention relates to a pressure ring assembly suitable for use in an electrical arc furnace, and more particularly, but not exclusively, to a pressure ring assembly suitable for use on a lower section of an electrode column.

[0004] Arc furnaces are frequently used in the steel and ferro alloy production industry during metallurgical smelting operations. An electric arc furnace comprises one or more electrodes that extend into a furnace. Lower ends of the electrodes are located adjacent a furnace load, and in use supply the required energy to melt the load by forming an electric arc between the electrode and the furnace load. The electric current required to achieve the arcing is conducted to the electrode by way of conductive contact shoes, which provide a conductive path between the energy source and the electrodes.

[0005] It will be appreciated that for optimal power conductivity, the contact shoes must at all relevant times be maintained in proper electrical contact with the electrodes. In order to maintain proper electrical contact between the contact shoes and the electrode during generally harsh operating conditions, a pressure ring is commonly arranged circumferentially about the contact shoes, and is configured and dimensioned to maintain a number of contact shoes in electrical contact with the electrode by urging the contact shoes towards the electrodes.

[0006] One type of pressure ring assembly commonly used in industry is a segmented pressure ring assembly, which comprises a plurality of arcuate pressure ring segments that are secured to one another in an end-to-end configuration in order to form a circular pressure ring assembly configured in use to extend around the electrode, with the contact shoes sandwiched between the electrode and the pressure ring assembly.

[0007] In existing designs, the pressure ring assembly includes a plurality of contact pads, generally one per pressure ring segment, which is used to apply a radially inwardly directed bias onto adjacently located contact shoes. This ensures that the contact shoe abuts the sidewall of the electrode in order efficiently to conduct electricity to the electrode. The contact pad is typically in the form of a circular plate that is displaceable relative to the body of the pressure ring segment. The contact pad is moveably secured to the pressure ring body by way of displaceable bellows, and pressurization of the volume between the pressure ring body, the contact pad inner surface and the bellows result in expansion of the bellows, and hence actuation of the contact pad.

[0008] An example of an existing pressure ring assembly and contact show arrangement is shown in Figures 1 and 2. The assembly typically includes a plurality of pressure ring segments 1 that are located end to end to form a closed loop about an electrode 9. Each pressure ring segment 1 is associated with a contact shoe 3 that is located between the pressure ring segment 1 and the electrode 9. The contact shoe 3 is a separate component and is urged away from the pressure ring segment 1 towards the electrode 9 by way of a displaceable contact pad 2, which is displaceably secured to the pressure ring segment, typically by way of bellows. Various configurations are used in practice, but in the configuration shown, a single hanger 4 is used to suspend both the pressure ring segment 1 and the associated contact shoe 3 from the upper structures of the electrode arrangement. Although the design is to some extent simplified by using a single hanger 4, the hanger is of complicated design due to the various parts having to be electrically isolated from one another. Separate coolant pipes 5, 6 feed cooling water to the pressure ring segment 1 and the contact shoe 3, and a separate electricity feed 7 furthermore provides electricity to the contact shoe 3. It is clear from Figure 1 how much space is taken up by water I electricity supply conduits, and how involved the design of the pressure ring assembly I contact shoe combination is. Functionally, the above configuration is tried and tested technology, but it is nevertheless associated with some disadvantages or at least areas where significant improvements can be made. This mostly relates to the fact that the pressuring ring assembly and the contact shoes are independent and discrete parts, resulting in certain shortcomings. The pressure ring and the contact shoes have to be in separate flow communication with a coolant, thus resulting in multiple pipes having to extend from the top end of the furnace to the pressure ring and the contact shoes. This increases cost, makes it more difficult and time consuming to install, maintain and remove the pressure ring and the contact shoes, and also takes up significant space. The pressuring ring segments and the contact shoes must also be independently suspended. Even in designs where a common hanger is shared (such as that shown in Figures 1 and 2), such a hanger has to be a complicated and expensive double insulated hanger if it is to carry both a pressure ring segments and a contact shoe. The combinations of the pressure ring segment, including a displaceable contact pad, and the separate contact shoe is also overly complex and costly, and it would be beneficial if the design could be simplified and at least some components omitted.

[0009] It is accordingly an object of the invention to provide a pressure ring assembly that will at least partially alleviate some of the above shortcomings.

[0010] It is also an object of the invention to provide a pressure ring assembly that will be a useful alternative to existing pressure ring assemblies.

[0011] SUMMARY OF THE INVENTION

[0012] According to the invention there is provided a pressure ring assembly including: a pressure ring segment; and a contact shoe; characterized in that the contact shoe is displaceably connected to the pressure ring segment. There is provided for the contact shoe to be connected to the pressure ring segment by way of a bellows arrangement.

[0013] There is provided for the pressure ring assembly to be devoid of a contact pad between the pressure ring segment and the contact shoe.

[0014] In a preferred embodiment, a cavity is formed between the pressure ring segment, the contact shoe and the bellows arrangement.

[0015] There is provided for the pressure ring segment to include a recessed zone, with the bellows and the contact shoe enclosing the recessed zone in order to define the cavity.

[0016] There is provided for the cavity to be in flow communication with a fluid source in order for the contact shoe to be outwardly displaceable when the cavity is filled with a fluid. In a preferred embodiment, the fluid is a coolant, preferably water.

[0017] A further feature of the invention provides for complementary protrusions to extend into the cavity from both the pressure ring segment and the contact shoe.

[0018] The protrusions may be in the form of elongate fin formations, with a fin formation extending from the pressure ring segment and a complementary fin formation extending from the contact shoe being aligned to form one substantially continuous fin formation when viewed in plan. There is provided for ends of the fin formations to be complementary shaped, for example stepped, to facilitate alignment between the ends of the complementary fin formations.

[0019] The fins formations are configured to be slidingly displaceable relative to one another when the contact shoe and the pressure ring segment is displaced relative to one another. There is provided for the complementary fin formations to define a serpentine flow path through the cavity, while also allowing electrical conductivity between the pressure ring segment and the contact shoe.

[0020] In one embodiment, three spaced apart fin formations extend from the pressure ring segment and three spaced apart fin formations extend from the contact shoe, so as to form three spaced apart combined fin formations.

[0021] There is provided for the pressure ring assembly to include a coolant supply conduit having an inlet at one end of the pressure ring segment, an outlet at an opposite end of the pressure ring segment, and a coolant flow path extending between the inlet and the outlet. There is provided for the cavity, and in particular the serpentine flow path flowing through the cavity, to be part of the coolant flow path.

[0022] There is also provided for the pressure ring assembly to include an electricity supply.

[0023] In one embodiment, the electricity supply is connected to the contact shoe only.

[0024] In another embodiment, the electricity supply is connected to the contact shoe and to the pressure ring segment. In this embodiment, there is provided for the electricity supply to be in the form of a pipe bus configured to supply water and electricity to the pressure ring assembly.

[0025] An end of the pipe bus may be connected to the inlet of the pressure ring segment, and a flexible conductor may extend between the pipe bus and the contact shoe.

[0026] There is provided for one end of the flexible conductor to be secured, preferably clamped, onto the pipe bus. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] A preferred embodiment of the invention is described by way of a nonlimiting example, and with reference to the accompanying drawings in which:

[0028] Figure 1 shows a side view of a part of an electrode arrangement as is known in the art, and in particular an existing pressure ring segment and contact shoe arrangement;

[0029] Figure 2 is a cross sectional side view of the pressure ring segment and contact shoe arrangement of Figure 1;

[0030] Figure 3 shows a comparative side view (to figure 1) of a part of an electrode arrangement in accordance with the present invention, and in particular a pressure ring assembly in accordance with the present invention;

[0031] Figure 4 is a comparative cross-sectional side view (to figure 2) of the pressure ring segment and contact shoe arrangement of Figure 3;

[0032] Figure 5 is a perspective view of the pressuring ring assembly in accordance with one embodiment of the present invention;

[0033] Figure 6 is an exploded perspective view of the pressure ring assembly of Figure 5;

[0034] Figure 7 is a top plan view of the pressure ring assembly of Figure 5;

[0035] Figure 8 is a cross-sectional side view of the pressure ring assembly of

[0036] Figure 5, taken through the middle of the pressure ring assembly; Figure 9 is a cross-sectional front view of the pressure ring assembly of Figure 5, taken through the cavity inside the pressure ring segment;

[0037] Figure 10 is a cross-sectional top view of the pressure ring assembly of Figure 5, taken through the middle of the pressure ring assembly;

[0038] Figure 11 is a perspective view of the contact shoe inside the contact shoe housing, seen from the operatively inside of the contact shoe;

[0039] Figure 12 is a perspective view of the contact shoe inside the contact shoe housing, seen from the operatively outside of the contact shoe; and

[0040] Figure 13 is a perspective view of the pressuring ring assembly in accordance with the invention installed around an electrode.

[0041] DETAILED DESCRIPTION OF INVENTION

[0042] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

[0043] Referring to the drawings, in which like numerals indicate like features, a nonlimiting example of a pressure ring assembly in accordance with the invention is generally indicated by reference numeral 10. The pressure ring assembly 10 is an integrated design that includes both the conventional pressure ring and the conventional contact shoe in the same integral unit. Figures 1 and 2, as discussed above, show an embodiment of a typical prior art design. Reference to “the figures” below accordingly refers to the embodiment as shown in Figure 3 to 13.

[0044] Referring now to Figures 3 to 13, the pressure ring assembly 10 in accordance with the invention includes a pressure ring segment 20, a contact show housing 30, a bellows 35 and a contact shoe 40.

[0045] The pressure ring segment 20, best seen in Figures 5 and 6, is typically made from a copper body 21 , with each segment having a curved configuration in order for multiple segments in use to define a continuous ring locatable around an electrode 9. The body 21 includes two operatively vertical sides 21.1 , an operatively upper, horizontal top end 21.2 and an operatively lower, horizontal bottom end 21.3. Connecting apertures 22, suitable for receiving a complementary connector 70, are provided in the body towards the sides 21.1 of the body. In use, the connectors 70 secure adjacent segments 20 to one another in order to define the continuous ring.

[0046] A recessed zone or cavity 23 is provided in a proximal zone of the body 21. A similar cavity is present in the prior art as well, where it houses the contact pad, but in this case the configuration and use of the cavity is different, as will be evident from the discussion below. A coolant passage 24, best seen in Figure 9, extends through the body, and more particularly extends between an inlet 24.1 and an outlet 24.2 provided in the body. The cavity 23 also forms part of the coolant passage 24. The part of the passage 24.3 extending through the cavity 23 is of a serpentine configuration, as is discussed in more detail below.

[0047] As is best seen in Figures 6 and 9, a plurality of fins or slats 25 extend from the inner face 23.2 of the cavity 23 towards the open end of the cavity. Each fin 25 has an elongate body 25.1 , with one side edge 25.3 located in the proximity of an edge 23.1 of the cavity. The opposite end of each fin 25, i.e. the end located towards the middle of the cavity 23, terminates in a formation suitable for allowing alignment and engagement with a complementary fin 43 extending from the contact shoe 40, such as a stepped end 25.2. Seen independently, the fins 25 protruding from the body 21 of the pressure ring segments 20, and more particularly from an inner face 23.2 of the cavity 23, already defines a serpentine flow path 24.3 through the cavity 23, but this is further augmented in use due to the complementary nature of the fins 25 extending from the pressure ring 20, and the fins 43 extending from the contact shoe 40, as described in more detail below.

[0048] A contact shoe housing 30 is shaped and dimensioned to fit inside the cavity 23. The housing 30 is of tubular configuration, with a profile matching that of the perimeter of the cavity 23. The housing is typically made from copper. A connecting ring 30.1 extends radially inwardly from an inner end of the housing 30. The connecting ring 30.1 is made from aluminium bronze, whereas the housing 30, as mentioned above, is made from copper. The material selection is important, because aluminium bronze can be secured to copper (material from which the housing 30 is made) and also to stainless steel (material from which the bellows 35 is made).

[0049] The pressure ring assembly 10 also includes a bellows 35, and as has been mentioned above, more particularly a stainless steel bellows 35. The bellows 35, best seen in Figures 8 and 10, forms the displaceable connection between the contact shoe 40 and the pressure ring segment 20. The design of this type of bellows 35 is well known in the art, although in this case the bellows 35 is of a rectangular configuration in order to match the profile of the contact shoe 40. Traditionally, where bellows is used to displace a contact pad 2, the bellows is of a circular configuration. The bellows 35 includes an inner end 35.1 , which is in use secured to the connecting ring 30.1 of the contact shoe housing 30, and an outer end 35.2, which is in use secured to the contact shoe 40.

[0050] The contact shoe 40, best seen in Figures 5, 6 and 11 , also takes the form of a copper body 44 having an operatively outer surface 41 which is configured to match the curvature of an electrode, and a flat operatively inner surface 42. The inner surface 42 of the contact shoe 40 defines one wall of the enclosed cavity formed between the cavity 23 in the pressure ring segments 20, the bellows 35 and the contact shoe 40, and as such is directly exposed to coolant flowing through the serpentine flow passage 24.3, which coolant also serves as actuation fluid to displace the contact shoe 40.

[0051] As is the case with the pressure ring segments 20, a plurality of fins or slats 43 extend from the inner face 42 of the body 44 towards the pressure ring segment 20. Each fin 43 has an elongate body 43.1 , with one end in use located in the proximity of an edge 23.1 of the cavity 23, but while leaving a gap between the fin 43 and the inside edge 23.1 , which gap defines a flow path for coolant. The opposite end of each fin 43, i.e. the end located towards the middle of the cavity 23, terminates in a formation suitable for allowing alignment and engagement with a complementary fin 25 extending from the pressure ring segment 20, such as a stepped end 43.2. Each fin 43 protruding from the contact shoe 40, and more particularly from the inner face 42 of the contact shoe, in use lines up with a fin 25 protruding from the pressure ring segment so as to form a substantially continuous fin. The purpose of this is twofold - it creates a serpentine flow path 24.3 through the cavity 23 (see figure 9), and hence adjacent the inner surface 42 of the contact shoe 40 which requires cooling in use, but also allows continuous electrical conductivity between the pressure ring segment 20 and the contact shoe 40 even though the two sections are displaceable relative to one another. It should be noted that due to the ample exposure of the contact shoe 40, and in particular the inner surface 42 of the contact shoe 40, to the cooling water, the contact shoe does not require additional internal cooling passages, and therefore also does not require independent coolant supply conduits. A single water feed accordingly provides sufficient cooling to both the pressure ring and the contact shoe, while also enabling actuation of the bellows driven contact shoe.

[0052] The installed pressure ring assembly 10 is shown in Figures 3, 4 and 13. If the installed configuration is compared to the prior art (Figures 1 and 2) the simplification is immediately apparent. In the embodiment shown in Figures 3, 4 and 13, a combined bus pipe I water riser 50 extends down the side of the electrode to the pressure ring assembly 10 and is connected to an inlet 24.1 of the pressure ring segment. A corresponding bus pipe I riser extends from the outlet 24.2 away from the pressure ring assembly. In the embodiment, the bus pipe 50 supplies water to the pressure ring assembly 10, while also conducting electricity to the pressure ring assembly 10. A flexible conductor 60 is clamped (via clamp 61) onto the bus pipe 50, and conducts electricity directly to the contact shoe 40. However, it will be appreciated that in this configuration, electricity will in addition also be conducted through the pressure ring body 21 , and through the fins (25 and 43) to the contact shoe 40.

[0053] In another embodiment it is also foreseen for electricity to be supplied directly to the contact shoe only, while water is supplied to the pressure ring only, and this embodiment falls within the scope of the invention. However, the illustrated example has the benefit of reducing the number of conduits, and the further advantage that when both components are live, no additional isolation between the two components is required to prevent arcing.

[0054] The flexible, clamped on, conductor 60 also result in a number of advantages. The fact that the connection is flexible, as opposed to the rigid bus pipe connections of the prior art, means that the contact shoe is allowed to be displaced evenly, and not in a slightly pivoting manner as is the case in the prior art where the connection is rigid and acts as a pivot point. This asymmetrically moving prior art configuration results in reduced contact area between parts of the contact shoe and the electrode, and increased wear at one end, whereas this is avoided when using the flexible conductor 60. The clamp on conductor also makes it easy to install and remove the pressure ring assembly, as it reduces the fixed (soldered) connections to one per pressure ring I contact shoe set - i.e. the bus pipe going into the pressure ring. In the prior art the connection to the contact shoe is also a rigid bus pipe (riser) combination, i.e. like the one still going into the pressure ring, and the configuration associated with the present invention is duplicated.

[0055] The new pressure ring assembly design results in a number of benefits. These include, but are not limited to:

[0056] The use of significantly less conduits and connectors, which is beneficial from an installation, cost, space and complexity perspective;

[0057] Doing away with an intermediate connecting pad (connecting cartridge) required in the prior art, which reduces cost and complexity; Simplification of installation and maintenance due to only one integrated unit having to be installed and maintained;

[0058] Use of a smaller diameter pressure ring (due to the omission of the pressure pad) resulting in reduced weight, and hence cost, and therefore also easier installation;

[0059] - A simpler process to install and remove - not only due to smaller and simplified combination, but also fewer conduits to disconnect;

[0060] Doing away with a separate hanger or integrated but double insulated prior art hanger required to retain the contact shoe in position;

[0061] - Addition of the option of energizing both the pressure ring segment and the contact shoe, with the design making provision for electricity to be conducted from the pressure ring to the contact shoe.

[0062] It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and / or the scope of the invention.

Claims

CLAIMS:1 . A pressure ring assembly including: a pressure ring segment; and a contact shoe; characterized in that the contact shoe is displaceably connected to the pressure ring segment, with a cavity formed between the pressure ring segment and the contact shoe.

2. The pressure ring assembly according to claim 1 wherein the contact shoe is connected to the pressure ring segment by way of a bellows arrangement.

3. The pressure ring assembly according to claim 1 or claim 2 wherein the pressure ring assembly is devoid of a contact pad between the pressure ring segment and the contact shoe.

4. The pressure ring assembly according to claim 2 wherein the pressure ring segment includes a recessed zone, with the bellows and the contact shoe enclosing the recessed zone in order to define the cavity.

5. The pressure ring assembly according to any one of the preceding claims wherein the cavity is in flow communication with a fluid source in order for the contact shoe to be outwardly displaceable when the cavity is filled with a fluid.

6. The pressure ring assembly according to any one of the preceding claims wherein complementary protrusions extend into the cavity from both the pressure ring segment and the contact shoe.

7. The pressure ring assembly according to claim 6 wherein the protrusions are in the form of elongate fin formations, with a fin formation that extends from the pressure ring segment and a complementary fin formation that extends from the contact shoebeing aligned to form one substantially continuous fin formation when viewed in plan.

8. The pressure ring assembly according to claim 7 wherein ends of the fin formations are complementary shaped, for example stepped, to facilitate alignment between the ends of the complementary fin formations.

9. The pressure ring assembly according to claim 7 or 8 wherein the fin formations are configured to be slidingly displaceable relative to one another when the contact shoe and the pressure ring segment is displaced relative to one another.

10. The pressure ring assembly according to any one of claims 7, 8 or 9 wherein the complementary fin formations define a serpentine flow path through the cavity, while also allowing electrical conductivity between the pressure ring segment and the contact shoe.

11. The pressure ring assembly according to any one of the preceding claims wherein including a coolant supply conduit having an inlet at one end of the pressure ring segment, an outlet at an opposite end of the pressure ring segment, and a coolant flow path extending between the inlet and the outlet.

12. The pressure ring assembly according to claim 11 wherein the cavity is located in the flow path.

13. The pressure ring assembly according to any one of the preceding claims wherein the pressure ring assembly includes an electricity supply.

14. The pressure ring assembly according to claim 13 wherein the electricity supply is connected to the contact shoe only.

15. The pressure ring assembly according to claim 13 wherein the electricity supply is connected to the contact shoe and to the pressure ring segment.

16. The pressure ring assembly according to claim 15 wherein the electricity supply is in the form of a pipe bus configured to supply water and electricity to the pressure ring assembly.

17. The pressure ring assembly according to claim 16 wherein the pipe bus is connected to the inlet of the pressure ring segment, and a flexible conductor extends between the pipe bus and the contact shoe.

18. The pressure ring assembly according to claim 17 wherein the end of the flexible conductor is secured, preferably clamped, onto the pipe bus.

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